body {
    min-width: 320px;
    max-width: 750px;
    margin: 0 auto;
    background-color: #f2f4f7;
}
a {
    text-decoration: none;
    color: #707070;
}
// 约束当屏幕大于 750px的时候 html 字体大小就不变化了
@media screen and (min-width:750px){
    html {
        font-size: 37.5px !important;
    }
}
.header {
    height: 2.133333rem;
    border-bottom: 1px solid #eaeaea;
    text-align: center;
    line-height: 2.133333rem;
    font-size: .933333rem;
    color: #1c1c1c;
}
.nav {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    .item {
        margin: 1.466667rem auto;
        width: 6.72rem;
        height: 6.72rem;
        text-align: center;
        img {
            width: 100%;
            height: 100%;
        }
    }   
}